


There's Always a Lighthouse

by NeverEnoughCats



Category: Undertale (Video Game)
Genre: Alternate Universe, Angst in between, But game still slips in here and there, F/F, Fluff and Crack, Frisk is a merperson and everyone else are either pirates or human, Gen, Magic still works, Mer!Frisk AU, One Word Prompts, Pirates, Post game (kind of), merfolk
Language: English
Status: In-Progress
Published: 2015-12-19
Updated: 2015-12-17
Packaged: 2018-05-07 06:32:09
Rating: Teen And Up Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 3,131
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5446688
Author URL: https://archiveofourown.org/users/NeverEnoughCats/pseuds/NeverEnoughCats
Summary: <blockquote class="userstuff">
              <p>He steps in deeper, waves licking up to his chest but he doesn't notice the shape twisting in the waters behind him. It flows with the current like it's part of it, claws flashing and curling as it waits for him to walk further out into the sea. When he takes another step, kicking up sand, a scream is cut short by a sudden meeting with water overhead,</p>
<p>It lunges - </p>
<p>"ow." is all Sans says, looking down at a grinning Frisk, arms wrap around his middle while their tail kicks wildly in glee at the successful tackle hug before the Pirate Queen attempts to suplex the merperson and him into the ocean.</p>
            </blockquote>





	There's Always a Lighthouse

**Summary for the Chapter:**

> In which If Sans could be a dragon or a king: he chooses to be a clam, Mettaton talks about legs and Toriel hugs the fishcake.

** If **

Sans perked up, opening an eye to look at the other. Frisk remained where they were, pose relaxed in the water and a small smile playing on their lips.

"Yeah? What do you mean, kid?"

Frisk smiled wider and raised their hands, damp fingers forming words again. Sans saw their tail, blue scales in the shade of the sky meets the sea and beyond while purple followed akin to stripes. Upon closer inspection, the stripes were actually patterns in swirls, going around the tail that swished lightly side to side.

_If you could be anything, what would you be?_

"What would I be, huh?" the lighthouse keeper – well, that was what Sans called it; Pap's 'Lighthouse Masters' was a mouthful and thus took too much effort to say – hummed as he leaned back onto the rock he sat on. Seawater splashed up onto his clothes when Frisk shifted to sit up and the thought that the rocky pool was much too small for the merperson rose up. Sans held onto that bubble of thought for a moment, making a note to look for a bigger one for Frisk later, before letting it float away. He returned to the question and sighed happily, winking at the merperson. "I'd say my brother but he's too cool for me, so probably a clam or something."

Their eyes widened at the mental image, putting Sans' face on a shellfish and Frisk rolled over in giggles, causing the water to splash around more. Sans found that he didn't mind too much, he was going to wash his clothes anyway.

_A clam? Would you have pearls then?_

"They're actually bits of sand, right?"

Sand enters the clam's mouth, they use their spit to cover it so it won't hurt their gums. Frisk explained with a nod, hints of many colors on the translucent webs between their fingers shifting under the sun. Sans eyed the little pieces of rainbows in their hands instead of listening, since he already knew how pearls worked. He briefly wondered if he and Pap' could find out what color Frisk preferred and decorate the new tide pool.

Then again, knowing Papyrus, he would just cover the rock edges with spaghetti and a pair of sunglasses on the biggest rock. As a guardian to watch over the merperson, of course.

_And then I eat it._

Sans blinked once, taking in the shapes Frisk's fingers made. "Sorry?"

Frisk pouted and the little fins in place for ears under their hair twitching, but Sans knew them well enough to tell that it was in false annoyance. _We eat pearls._

Huffing, he raised a brow at them. "Really?"

_They make our scales shinier._ the merperson gestured with a nod and Sans entertained the idea of calculating the price for a fresh pearl, but stopped because the effort of thinking about that thought was too much. He settled for just sitting up a little straighter to show his curiosity. _But they are really hard to come by. Most of them are too small or harvested by –_

Frisk stopped in a motion for human, a frightened wide-eyed glance at the other for his reaction. Sans just shrugged and threw a smile at them, making sure not to move too quickly in case it scared them away. He waited, watching the tension leave Frisk's shoulders at the absence of expected anger and then slowly reached out a hand.

They tried to hide their flinch but Sans noticed anyway, hand lowering to poke at the water below instead.

_Humans get angry very quickly._ Frisk had once mentioned, arms crossed to hold themself while pointedly facing away from Sans and his brother.

Sans noticed that they also made an effort not to look at the ocean either, but did not bother asking. Frisk would tell them in their own time.

A few heartbeats passed, well-used on observing how Frisk had lined the seashells that Papyrus collected for them around the rock edges of the pool, when Sans felt a something cool nudged his palm. He let them intertwine their fingers, his rough human digits against Frisk's smooth, clawed ones. Frisk was always careful with their claws, so he let them and ignored the slime on the webbing, lightly brushing a thumb across the trail of scales on the back of the merperson's hand.

Neither of them spoke, letting the silence rest on them while the sea sighed and the gulls call above. It felt timeless, a moment Sans would take and lock away somewhere safe if he could but he couldn't, so he did the next best thing he could think of.

"Hey, kid."

They inclined their head towards him, tail swishing lightly into a more comfortable position. Yeah, he should really get them a new pool despite how small they were.

"Guess you could say clams that wake up before sunrise," Sans paused, his grin growing ear to ear, "wake up pearly in the morning."

Frisk twisted around to shoot him an offended look but the upward tips of their lips diminished most of its effect. They let out a laugh, sliding low into the pool so that the water covered their face and turned sound into bubbles.

Sans simply snorted at the amount of bubbles covering the merperson's expression, not noticing his cheeks hurting. "You don't think so? Unbeliev-bubble."

More bubbles from badly muffled giggles, their headfins shifting from laughing so hard. Frisk used their free hand to splash some water at him in attempt to stop him.

"Alright, alright, I'll save the rest for later." He relented and shifted so he could use his other hand to ruffle their hair.

Except Frisk's hair was really wet and braided with tiny seashells, making it harder to ruffle but it was the thought that mattered. He settled back on the rock and closed his eyes, enjoying the sun on his skin and the company when a tug on his damp sleeve made him look down.

Frisk touched their lips with their fingers, before lowering it in his direction. Sans chuckled and winked at them. "Did you just blow a kiss at me, kid?"

The merperson made a noise, slapping his arm lightly and hints of color blossomed on their cheeks and tips of their ears.

Sans laughed quietly again, earning another smack. "I know, I know."

Huffing, Frisk pouted and sunk back into the water to hide their embarrassment. The hand holding his squeezed lightly and he blinked, almost forgetting that they've still had yet to let go.

"Oh yeah," Sans said after a long moment, watching the ocean. Papyrus should be finished with his puzzles by now and on his way to come find them any minute now. Frisk didn't react to his words, busy inspecting his captured limb. They still found how it fascinating how their skin became soggy from being in the water for awhile, but he knew they were listening. "What 'bout you?"

They gave him a confused look.

"If you could be anything."

Frisk blinked and raised a hand to sign, but stopped and dropped it gently back into the water. Sans raised a brow in question, but they simply shook their head and smiled as brightly as they could.

He squeezed their hand back.

* * *

** Legs **

Singing was fun.

Frisk didn't use actual words, preferring to just sing meaningless tunes or hum to the melody. Shyren seemed to understand, much to their delight, and it helped Napstablook with their remixes. Still, they didn't exactly know how to react to Mettaton asking them to join his crew.

"Imagine, a merperson on our show!" the robot exclaimed in excitement, stars in his eyes. Frisk and Shyren both leaned back slightly to avoid the bright flare while Blooky faded away into the background. "They will love it and while everyone already loves me, I'm sure they will gladly make room for you in their hearts, darling."

Frisk nodded with grave seriousness, doing their best to give Mettaton their attention until the robot shifted forward to strike a pose.

Their attention just dropped from his face to his lower half. More specifically, the shiny smooth metal shaped in perfection, fitted with really tall neon pink at the ends.

Frisk stared at it, their tail fins twitching.

They wanted to touch it.

" – and we could even put glitter in your tank if you want to. Or get Doctor Alphys to make a cross between a wheelchair and a bathtub, I'm sure she wouldn't mind." Mettaton paused and gave a dazzling smile. "And yes. I know my legs are perfect, starshine."

Grinning sheepishly, Frisk quickly pulled their hand back, grimacing slightly at the water they left on the robot's leg and quickly signing. _Sorry._

"Don't worry about it, darling. Alphys made them water-proof in case we ever did a water game during a show." Mettaton brushed off their concerns with a wave of a perfectly manicured hand. Shryren and Blooky had left at some point, probably to get more snacks. "We will use Burgerpants as the target."

_How,_ Frisk bit their lips and slowly moved their fingers, _What is it like to have legs?_

"Hmm, that's a good question." Mettaton seemed to consider their words, gracefully sitting down the a beach chair Toriel brought for visitors to use. It wasn't a throne but Mettaton had this natural way of making even the ugly green and yellow chair look pleasant enough when it supported him. "Well, the best way to put it is that it's another piece of you, starshine."

Frisk snorted.

"Which is, of course, basically logic." Explained the glamorous robot, warm air leaving his system in the form of a sigh. "What I mean is that it's there to take you to where you want to go, much like those human sayings to keep going no regardless of what happens." He then frowned lightly and crossed his legs, gazing at them in bemusement. "At the same time, they also can weight you down."

"You have to have the energy to keep them moving, like your tail." Mettaton gestured to Frisk and nodded sagely, "which is a beautiful masterpiece of colors FYI, dear, but back to the topic."

They nodded in agreement and sat up straighter.

"It's difficult to swim when you're tired, yes?"

Frisk nodded slowly. It was obvious, everyone didn't like moving when they were tired, or just really lazy. Sans was the perfect example for the latter.

"Same for legs, except I run on batteries and don't experience the same fatigue as the rest of you. Sometimes they would be so heavy that they don't work at all."

_Are they a burden?_ Frisk didn't like the idea of legs being a bother. It allowed the owners to do so many things, why would they ever be troublesome?

"It might feel that way for a little while, but I'd say never." Mettaton leaned back into the chair – demonstrating incredible balance by not falling over – and raised a leg on point, the metal glimming in the light like polished diamond. "I would never give these babies up even if it costed me my life!"

Mettaton watched with content as the merperson burst into giggles at his claim, waiting for them to settle down before continuing. "But really, to have legs is to have a way to keep going until you've archived your dreams."

_So legs help you reach goals?_

"Yes. However," the robot reached out with one of his extendable arms – 'noodle arms' Papyrus once told them but Frisk was pretty sure there was a scientific name for them. Maybe they should ask Sans or Mom – and gently poked Frisk on the nose – they were pretty sure it was called a boop, scientific or not – with a smile. "This does not mean you can't do the same just because you don't have 'proper duo legs'. Even when I didn't have limbs, I still found a way."

"In conclusion, both legs and fins give you the opportunity to travel to new places. In a way it doesn't matter whether or not you can walk or swim or float, they both help you reach your goals, darling."

"I should write a book." Mettaton nodded happily, then stopped and narrowed his eyes in realization. "Wait, that last bit contrasts what I've said at the very beginning."

Frisk made a confused noise and the robot sighed, reaching behind the beach chair to a basket the merperson never noticed existed until then. "Well, plan B then."

He pulled out an egg and cracked on his leg.

It started to sizzle.

* * *

  
**Nightmare**

A golden flower smiled up at them, laughed when the ring of white closed in on them. They didn't care, barely giving the dark corner where it landed a glance. Soft warmth held their hand. Fire around them, but she never got a chance. The first move was always theirs. They left the door ajar and a kicked pile of dust behind.

Cold. Their fingertips quickly became numb but they didn't bother, digging out chucks of the talking snowman. The comedian and his brother tried to talk to them and do puzzles. Ignored.

_They're not worth your time._

The tall monster waited for them. It kept talking, so they stepped on its skull to shut it up. They left an empty town and a dusty scarf behind.

Damp and rushing water. They stood at the edge of the river and stared for a long time, before walking away. A statue they dismiss, a pathetic monster with no arms. They put the thing out of its misery and the knight stopped them.

It died and came back.

It died again and made a smart decision not to return. Clever.

Too hot, but they gritted their teeth and keep going. A laboratory and a talking calculator. It would be a stroll in the park, if the park was built on lava and steam. They laughed at two lovers and made sure to kick their dust over into the heat below.

The core, not as burning as outside but still unwelcomed. The calculator grew legs, but that didn't save it. They left a dying powerplant and broken pieces of metal behind.

They kept going. An old house, the flower talked and talked and their knuckles were white from gripping the knife. Annoying. A gold corridor, bells towing and the comedian was there.

It stood in your way.

At least this one wasn't as boring as the rest. All the rest did was just stand there and die, at least this one made it fun. It had the first turn instead, surprising them enough to get hurt but they had to keep going.

You raised the knife, face hurting from smiling so much at the snoring skeleton and –

Bring it down into your gut.

There was pure rage and a force trying to wrestle your hand away from the blade, but you sink it deeper and managed to even twist it before ––

They woke up.

It was really the pain that startled Frisk awake. They kicked out, tail hitting smooth rock and seaweed. Dark water disoriented them and for a moment, they held their breath as if they couldn't breathe, as if they were human. Against their instincts, Frisk dragged themself out of the water , gills flexing as they coughed loudly.

They glanced around after a few harsh breaths, finding the little cove and the door to Toriel's house. Not a corridor with polished floors and tall windows. As vivid as the dream was, the merperson knew that place was something they would only see in photos or Alphys' comic books. Knowing that fact brought relief to them.

Still shaking, Frisk started to lower their body back into the pool when a jolt of pain made them jerk. There was red on their stomach, under their claws and in the water. Copper overwhelmed their senses and they snorted sharply, trying to get the smell out of their head.

Seaweed would do for now – Frisk had gotten used to the sting of salt long ago – since they didn't want to wake their mom up just because of a small wound but the blood wouldn't stop flowing despite how hard they pressed on it.

"Child?" They yelped at the voice, having not noticing the footsteps and quiet crick of the door. Frisk twisted away from the edge and flopped back into the water, curling up into themself while trying not to cry out in pain.

Toriel stood at the open door, lantern glow revealing her features furrowed in concern. She walked over to the pool, uncaring of her bare feet and water soaking her nightdress as she kneeled down. "Are you alright, my child? Did something happen?"

Of course their mom would notice. She always seemed to know when Frisk needed her unlike some people, something the merperson adored with the barest hint of bitterness.

Frisk hesitated, hands clenched lightly but they shift upwards. _Bad dream_ , they signed and winced at Toriel's worried murmur. The weeds weren't doing too well, their claws must had sunk in deeper than they thought.

Their mother muttered under her breath, setting the lantern down on the edge and motioning for them to wait before she went back into the house. It was still really early, a piece of the still dark sky peeking in through the crack on the cove's ceiling. She must be so tired.

Frisk frowned while climbing back onto the edge. Toriel stayed up late that night to finish marking the test papers and they remembered one of her students causing her trouble. They would apologize when she came back, Frisk decided and curled up, careful to avoid their injured side. They start to drift back to sleep, tail in the water and the warm glow of the lantern for company.

They woke up again, this time to their mom shifting them into her arms. Their stomach felt numb, bandages tight around their waist and Frisk could see a small first-aid kit next to the lantern. Toriel had changed her nightdress for a pastel-colored swimsuit, Frisk would comment on how pretty it was but a yawn interrupted them.

"Do you want to talk about it?" Toriel murmured kindly into their hair as she stepped into the shallow part of the pool and sat down with them in her arms.

Frisk just shook their head and nuzzled her, managing to awkwardly curl their tail around their mother's legs.

"Very well, dear child." She breathed, holding them closer and the merperson sighed in delight at the warmth. "Rest, I'll protect you and your dreams."

Frisk used a finger to carefully draw a heart on Toriel's bare arm, followed by another gentle nuzzle.

Toriel answered with a kiss on their forehead and smiled softly.

**Notes for the Chapter:**

> Frisk was signing 'Thank you' in If (tip of fingers to lips and outwards to person, like blowing a kiss).
> 
> I'm planning to post three words for every chapter, so feel free to give me suggestions on what you want to see written. Comments are dipped in love and cuddled because I wanna know what you're think. Thanks for reading!

**Author's Note:**

> Inspired by [this](http://fofufofu.tumblr.com/post/133622205953/mermaid).


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